We already know that inflammation is the likely cause of a multitude of health conditions, including arthritis, asthma, cancer, chronic pain, headaches, depression, and heart disease.

Many experts believe that inflammation begins in the gut. Having a healthy digestive system is important because a healthy system filters out things that can damage it (like bad bacteria, toxins, chemicals, and waste products). It also helps us absorb and deliver the good stuff like nutrients from our food.

About 70% of our immune cells are in our digestive system, and they make direct contact every bit of food we consume. If the immune system is triggered by bacteria in food, flags a food as an allergen, or has an imbalance of important hormones such as insulin, it can cause inflammation.

As you can imagine, everything you eat or drink affects your intestinal bacteria, and is likely to ultimately have an impact on your health.

A new large-scale study led by RUG/UMCG geneticist Cisca Wijmenga into the effect of food and medicine on the bacterial diversity in the human gut, which is published this Friday in the research journal Science, provides more support for the gut bacteria-health link.

For this study, researchers collected stool samples from more than 1,100 participants in the LifeLines programme, which monitors the health of 165,000 residents of the Northern Netherlands. The samples were used to analyze the DNA of the bacteria and other organisms that live in the gut. In addition to stools, the study collected information on the participants’ diet, medicine use, and health.

The researchers said this study is unique: while previous research focused on patients with specific illnesses, this study focused on a group of normal people. In addition, the study covered an exceptionally large group of people and studied their gut DNA in detail.

Wijmenga explains:

Normally researchers only investigate one particular region of DNA in which different groups of bacteria can be distinguished. We have mapped all the bacterial DNA to gain much more detailed information about bacteria types.

Coffee, yogurt, buttermilk, and wine

This DNA analysis made it possible to examine which factors impact the diversity of the microbiome (the intestinal bacterial community unique to each of us).

And that appears to be many.

Wijmenga says, “You see, for example, the effect of diet in the gut.”

People who regularly consume yogurt or buttermilk have a greater diversity of gut bacteria. Coffee and wine can increase the diversity as well, while whole milk or a high-calorie diet can decrease it.

UMCG researcher Alexandra Zhernakova elaborates:

In total we found 60 dietary factors that influence the diversity. What these mean exactly is still hard to say. But there is a good correlation between diversity and health: greater diversity is better.

Diet isn’t the only factor that influences microbiome diversity: at least 19 different kinds of medicine – some of which are widely used -have an impact as well. An earlier study by Groningen researchers has shown that antacids decrease this diversity, while antibiotics and the diabetes drug metformin also have an effect.

Wijmenga stresses that these are important findings:

Disease often occurs as the result of many factors. Most of these factors, like your genes or your age, are not things you can change. But you can change the diversity of your microbiome through adapting your diet or medication. When we understand how this works, it will open up new possibilities.

Recent research has demonstrated that it is now possible to combat obesity through a “fecal transplantation” in which the intestinal bacteria from a slender person are introduced into the gut of an obese patient. An appropriate diet or a specific medicine may produce the same effect on the microbiome.

Currently a lot of research is focused on the microbiome, but it often seems hard to reproduce. It is therefore striking that the results of a Belgian group – published in the same issue of Science – show about 80 percent agreement with those of the Groningen group.

Wijmenga concludes:

The key is the way the research was done. What was important was that the stool samples were frozen immediately by the participants themselves, and picked up by the researchers while still frozen. When samples are sent in by post, as is often the case, you expose them to oxygen and high temperatures. These are conditions that some bacteria can’t survive in. These two Science articles have therefore set a new standard for future research in this field.

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